Self righting container

ABSTRACT

A self righting fluid container having a flanged neck portion, a weighted base portion and an intermediate tapered section connecting the neck portion to the base portion. The center of gravity of the container, whether filled or empty, is along the centerline of the container on the positive side of a critical line which line extends normal to the horizontal plane of the support surface on which the container rests from a point where the container contacts the support surface and where the base portion intersects the tapered section.

CROSS REFERENCE TO RELATED APPLICATIONS

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STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

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THE NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT

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INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC

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BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to fluid holding containers; and, more particularly, to a bottle which is self righting when tipped whether full or empty.

2. Description of the Prior Art Including Information Disclosed Under 37 CFR 1.97 and 1.98

Self righting bottles or containers are well known in the art. In U.S. Pat. No. 4,096,966 to Korshack, one such self righting container is disclosed in the form of a cup. Although Korshack attempts to find critical relationships between the cup diameter, the cup height, the small diameter of the base circular portion, and the diameter of the convex or part spherical portion at the lower portion of the cup, there is no teaching to apply to any container for self righting the same. Korshack's teachings are limited to a cup of the critical dimensional ratios set forth in his patent. In U.S. Pat. Nos. 4,303,170 and 4,388,996, Panicci discloses a self righting cup having a lower hemispherical portion and an upper portion of generally cylindrical form. Ratios are set forth for making a cup self righting. Again, only specific ratios are set forth for the cups of Panicci. There are no teachings that are applicable to any fluid filled container.

BRIEF SUMMARY OF THE INVENTION

It is an object of this invention to provide a self righting fluid containing container.

It is a further object of this invention to provide parameters for making any fluid containing container self righting.

These and other objects are preferably accomplished by providing a self righting fluid container having a flanged neck portion, a weighted base portion and an intermediate tapered section connecting the neck portion to the base portion. The center of gravity of the container, whether filled or empty, is along the centerline of the container on the positive side of a critical line extending normal to the horizontal plane of the supporting surface on which the container rests from a point where the container contacts the support surface and the base portion intersects the tapered section.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a vertical view of a self righting container in accordance with the invention disposed on a supporting surface;

FIG. 2 is a vertical view, partly diagrammatic, of the container of FIG. 1 shown in a totally inclined position;

FIG. 3 is a vertical view of a modification of a portion of the container of FIGS. 1 and 2;

FIG. 4 is a perspective view of a portion of the spray nozzle top of FIG. 3;

FIG. 5 is a vertical diagrammatic view of the stem section alone of the container of FIGS. 1 to 4;

FIG. 6 is a graph of the curve of the stem section of FIG. 5;

FIG. 7 is a diagrammatic illustration of the geometry of the fluid base portion 11 alone of the container of FIGS. 1 to 3;

FIG. 8 is a diagrammatic illustration of the geometry of the weighted member 19 alone of the container of FIGS. 1 to 3;

FIG. 9 is a diagrammatic illustration of the shifting center of gravity of the container of FIGS. 1 to 3;

FIG. 10 is a diagrammatic illustration of the geometry of a partially filled container of FIGS. 1 to 3;

FIG. 11 is a view taken along lines 11-11 of FIG. 10; and

FIG. 12 is a graphical illustration of the geometry of the container of FIGS. 1 to 3.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to FIG. 1 of the drawing, a container 10 is shown in the form of a bottle for convenience of illustration. For purposes of computation, “bottle” or “container” may be used to refer to container 10. Container 10 has a rounded 10 bottom base portion 11, a neck portion 12, and tapered section 13. Container 10 is hollow so that it is adapted to contain a liquid 14 therein. Container 10 may also be transparent and of glass or plastic or the like. Neck portion 12 is thus closed off by a cap 15. Cap 15 may be threaded onto mating threads at the top of neck portion 12 or snapped onto a flange thereon as is well known in the container art so as to provide a fluid tight fit. Base portion 11 may have a generally flat bottom wall 16 (FIG. 2) for resting on support surface 17.

As particularly contemplated in the invention, self righting means are provided for self-righting container 10 if it is rocked or moved off of the upright position shown in FIG. 1, such as the inclined position shown in FIG. 2.

Thus, referring again to FIG. 1, such self-righting means includes an annular flange 18 on the bottom of cap 15 and a weighted member 19 at the bottom of base portion 11.

As seen in FIG. 2, an angle a is provided between the plane of surface 17 and the centerline 20 through container 10. This angle a is identical to angle a between a line 21 perpendicular to the plane of support surface 17 (beginning where the tip 24 of base portion 11 touches surface 17) and a line 22 extending from the point of intersection of line 21 with the plane of surface 17 to the tip 23 of the base portion 11 (i.e., where tapered section 13 merges into base portion 11). Note that tips 23, 24 lie along line 22 which is coincident with the perimeter of container 10 where base portion 11 merges into tapered section 13.

As seen in FIG. 2, line 21 is to the left of the center of gravity located at point 26. This point 26 is on the positive side of critical line 21 (on the right side of line 21 in FIG. 2). A positive restoring moment occurs when point 26 is on the positive side of the critical line 21. When such a positive restoring moment exists, container 10 rights itself. Container 10 will not right itself if the center of gravity or point 26 is on the negative side of the critical line 21 or on the critical line 21. The critical line 21 extends vertically from the point 24 where the truncated hemisphere base portion 11 of the container 10 contacts the horizontal surface 17. For a restoring moment to exist, the center of gravity point 26 of the entire container 10, including the fluid, must be on the positive side of the critical line 21. This is true for any fluid level and any tilt position. The base section 11 of the container 10 is a truncated hemisphere. The smooth exterior surface of the base portion 11 allows the container 10 easy transition from the tilted position of FIG. 2 to its upright position in FIG. 1. The stem or tapered section 13 tapers in toward the center line 20 of the container. The taper of section 13 serves to minimize the container volume on the negative side of the critical line 21.

Cap 15 may be replaced with a spray nozzle, if desired. The cap flange 18 serves as a grip support and as a maximum tilt limiting device. The cap flange 18 determines the angle at which the bottle will rest when it is tipped completely on its side. Increasing the radius of flange 18 effectively reduces the size of the weighted member 19 required. This is important since it is not desirable to have an excessively heavy container, full or empty.

Preferably, container 10 is thin walled. With a thin wall, the weight of the container can be ignored in the tapered section 13 and base section portion 11 since the fluid weight is much greater. The weighted member 19 is preferably of a high density material, such as lead. The use of a high density material for the weighted member 19 contributes to minimizing the volume of the weighted member 19.

The center of gravity 26 of the entire container 10 and fluid, where i=the material of container 10, is given by:

$y = \frac{\Sigma \; y_{i}m_{i}}{\Sigma \; m_{i}}$

-   -   where y_(i)=is distance to center of gravity or point 26 of         element i as measured from the coordinate center, and     -   m_(i)=is the mass of element i.

The bottle is divided into four sections for the purpose of calculating the center of gravity and mass. The four parts are the cap section 15, the stem section 13, the fluid base section 11, and the weighted section 14.

Cap Section 15

The cap section includes the threaded portion of the container 10, the cap flange 18, and the cap 15 (or spray nozzle). As seen in FIG. 3, instead of cap 15, a spray nozzle top 29 is provided having a cap portion 30 threaded via threads (FIG. 4) onto neck portion 12, and a sprayer portion 31. The center of gravity is indicated at point 32, a distance y from the bottom horizontal plane 33 of flange 18 to the plane 34 parallel thereto. This analysis will discuss a nozzle end as in FIG. 3 as this would represent the worst case. The total mass of the cap section 15, 18 (or 18, 29) is the sum of the weights of the individual components. The weight of the cap flange 18 and threaded neck portion 12 are approximated based on a simplified component geometry and knowledge of the container material density (FIG. 4).

The mass of the cap threads and flange section is given by:

m _(f/t)=ρ_(container)π(t _(f)(r ² _(flange) −r ² _(cap)+2kzr _(cap))

-   -   where ρ_(container)=density of the container material

The mass of the spray nozzle top 29, m_(nozzle), is estimated at 001 lbs. The center of gravity for the nozzle top 29 is estimated at one inch above the flange base line 33 (FIG. 3). The center of gravity of the cap section relative to the coordinate center is given by:

Y _(cap)=1+L+n

-   -   The total mass of the top 29 is given by:

m _(cap) =m _(nozzle) +m _(f/t)

M_(nozzle) is the mass of the spray nozzle portion 31 with M_(cap) being the total mass of top 29.

Stem Section

The mass and center of gravity of the stem section (neck portion 12 and tapered section 13) are found by integrating along its length. The stem section 12, 13 is divided into two portions, a straight portion 12 and a curved portion 13. To facilitate the integration of the curved portion 13, a non-dimensional fourth order polynomial is used to define the changing stem radius along the length of the stem section 12, 13. The use of a non-dimensional expression allows variation in the container geometry without reevaluating the polynomial coefficient as shown in FIG. 5.

The fourth order polynomial of r(y) is given as:

$r = {{\left( {r_{\max} - r_{cap}} \right)\left\lbrack {a - {b\left( \frac{y}{L} \right)} + {c\left( \frac{y}{L} \right)}^{2} - {d\left( \frac{y}{L} \right)}^{3} + {e\left( \frac{y}{L} \right)}^{4}} \right\rbrack} + r_{cap}}$

The coefficients for the particular polynomial used in the preliminary design are presented in Table 1.

-   -   Table 1 Polynomial coefficients         -   r coefficients             -   a=0.99850             -   b=3.6699             -   c=6.2854             -   d=5.5478             -   e=1.9314

A plot of the non-dimensional polynomial is presented in FIG. 6 where r*=r/r_(max)−r_(cap)).

r*=0.99850−3.6699y/L+6.2854(Y/L)̂2−5.5478(Y/L̂3+1.9314(y/L)̂4R̂2=1.000

The distance to the center of gravity of the curved portion 13 of the stem 12, 13 is given by:

${\overset{\_}{y}}_{{stem}\mspace{14mu} {curve}} = {{\frac{\int{y{V}}}{\int{V}}\mspace{14mu} {where}\mspace{14mu} {V}} = {\pi \; r^{2}{y}}}$

Substituting in the equation for r the integral becomes:

${\overset{\_}{y}}_{{stem}\mspace{14mu} {curve}} = \frac{\int_{0}^{L}{y\left\{ {{\left( {r_{\max} - r_{cap}} \right)\left\lbrack {a - {b\frac{y}{L}} + {c\left( \frac{y}{L} \right)}^{2} - {d\left( \frac{y}{L} \right)}^{3} + {e\left( \frac{y}{L} \right)}^{4}} \right\rbrack} + r_{cap}} \right)^{2}{y}}}{\int_{0}^{L}{\left\{ {{\left( {r_{\max} - r_{cap}} \right)\left\lbrack {a - {b\frac{y}{L}} + {c\left( \frac{y}{L} \right)}^{2} - {d\left( \frac{y}{L} \right)}^{3} + {e\left( \frac{y}{L} \right)}^{4}} \right\rbrack} + r_{cap}} \right)^{2}{y}}}$

The center of gravity of the straight portion of the stem section is given by:

${\overset{\_}{y}}_{{stem}\mspace{14mu} {straight}} = {{\frac{\int_{L}^{L + n}{y{V}}}{\int_{L}^{L + n}{V}}\mspace{14mu} {where}\mspace{14mu} {V}} = {\pi \; r^{2}{y}}}$

The straight portion of the stem of the radius is constant and is given by:

r=r_(cap)

After substituting the integral becomes:

${\overset{\_}{y}}_{{stem}\mspace{14mu} {straight}} = \frac{\int_{L}^{L + n}{y\; \pi \; r_{cap}^{2}{y}}}{\int_{L}^{L + n}{\pi \; r_{cap}^{2}{y}}}$

The mass of the fluid in the curved portion 13 of the stem section 12, 13 is given by:

m _(stem curve)=∫₀ ^(L) ρdV where dV=πr ² dy

Substituting in the equation for r the integral becomes:

$m_{{stem}\mspace{14mu} {curve}} = {\int_{0}^{L}{\rho_{fluid}\pi \left\{ {{\left( {r_{\max} - r_{cap}} \right)\left\lbrack {a - {b\frac{y}{L}} + {c\left( \frac{y}{L} \right)}^{2} - {d\left( \frac{y}{L} \right)}^{3} + {e\left( \frac{y}{L} \right)}^{4}} \right\rbrack} + r_{cap}} \right)^{2}{y}}}$

The mass of the fluid in the straight portion of the stem section 12, 13 is given by:

m _(stem straight)=∫_(L) ^(L+n)ρ_(fluid) πr _(cap) ² dy

The total mass of the stem section 12, 13 is given by:

m_(stem)=m_(stem curve)=m_(stem straight)

The center of gravity for the entire stem section 12, 13 is given by:

${\overset{\_}{y}}_{stem} = \frac{{{\overset{\_}{y}}_{{stem}\mspace{14mu} {straight}}m_{{stem}\mspace{14mu} {straight}}} + {{\overset{\_}{y}}_{{stem}\mspace{14mu} {curved}}m_{{stem}\mspace{14mu} {curved}}}}{m_{{stem}\mspace{14mu} {straight}} + m_{{stem}\mspace{14mu} {curved}}}$

Base Section

The fluid base portion 11 consists of a truncated hemisphere (FIG. 7). The hemisphere radius is equivalent to the maximum radius of the stem section 12, 13. The location of the center of gravity for the fluid base portion 11 is given by:

${\overset{\_}{y}}_{{fluid}\mspace{14mu} {base}} = \frac{\int_{0}^{r_{\max - b}}{y{V}}}{\int_{0}^{r_{\max - b}}{V}}$

-   -   where dV=πr²dy and r=√{square root over (r_(max) ²−y²)}

After substituting, the center of gravity location integral becomes:

${\overset{\_}{y}}_{{fluid}\mspace{14mu} {base}} = \frac{\int_{0}^{r_{\max - b}}{y\; {\pi \left( {r_{\max}^{2} - y^{2}} \right)}{y}}}{\int_{0}^{r_{\max - b}}{{\pi \left( {r_{\max}^{2} - y^{2}} \right)}{y}}}$

The mass of the base portion 11 is given by:

m _(fluid base)=ρ_(fluid)∫₀ ^(r max−b) dV

Which upon substitution becomes:

m _(fluid base)=ρ_(fluid)∫₀ ^(r max−b)π(r _(max) ² −y ²)dy

Weighted Section

The weighted section or member 19 of the container 10 is formed by a spherical segment located just below the fluid base section (FIG. 8).

The location of the center of gravity for the weighted section or member 19 is given by:

${\overset{\_}{y}}_{weight} = \frac{\int_{r_{\max - h}}^{r_{\max - h + 1}}{y{V}}}{\int_{r_{\max - h}}^{r_{\max - h + 1}}{V}}$

-   -   where dV=πr²dy     -   and r²=r^(2max−y)2

Substituting the center of gravity location integral becomes:

${\overset{\_}{y}}_{weight} = \frac{\int_{r_{\max - h}}^{r_{\max - h + 1}}{y\; {\pi \left( {r_{\max}^{2} - y^{2}} \right)}{y}}}{\int_{r_{\max - h}}^{r_{\max - h + 1}}{{\pi \left( {r_{\max}^{2} - y^{2}} \right)}{y}}}$

After integrating the equation reduces to:

${\overset{\_}{y}}_{weight} = \frac{\begin{matrix} {{6{r_{\max}^{2}\left\lbrack {\left( {r_{\max} - h + t} \right)^{2} - \left( {r_{\max} - h} \right)^{2}} \right\rbrack}} -} \\ {3\left\lbrack {\left( {r_{\max} - h + t} \right)^{4} - \left( {r_{\max} - h} \right)^{4}} \right\rbrack} \end{matrix}}{{12r_{\max}^{2}r} - {4\left\lbrack {\left( {r_{\max} - h + t} \right)^{3} - \left( {r_{\max} - h} \right)^{3}} \right\rbrack}}$

The mass of the weighted member 19 is given by:

m _(weight)=ρ_(weight)∫_(r max−h) ^(r max−h+1) dV

Which upon substitution becomes:

m _(weight)=ρ_(weight)∫_(r max−h) ^(r max−h+1)π(r _(max) ² −y ²)dy

After integrating, reduces to:

$m_{weight} = {\rho_{weight}\frac{\pi}{3}\left( {{3r_{\max}^{2}t} - \left\lbrack {\left( {r_{\max} - h + t} \right)^{3} - \left( {r_{\max} - h} \right)^{3}} \right)} \right.}$

Full Container Stability

The center of gravity of the entire container and its fluid contents is given by:

${\overset{\_}{y}}_{bottle} = \frac{{{- {\overset{\_}{y}}_{cap}}m_{cap}} - {{\overset{\_}{y}}_{stem}m_{stem}} + {{\overset{\_}{y}}_{{fluid}\mspace{14mu} {base}}m_{{fluid}\mspace{14mu} {base}}} + {{\overset{\_}{y}}_{weight}m_{weight}}}{m_{cap} + m_{stem} + m_{{fluid}\mspace{14mu} {base}} + m_{weight}}$

The negative signs in the equation are in keeping with the sign convention for the specified coordinate system. The variable h can be written in terms of the specified variables as follows:

h=r _(max) +t−√{square root over (r _(max) ² −r _(base) ²)}

For the container 10 to return to its upright position, the center of gravity 26 of the entire container 10 must be on the positive side of the critical line 21 (i.e., y bottle>y critical). When the container is full, the center of gravity 26 is essentially on the center line 20 of the container 10 for all tilt angles. The center of gravity distance is a measure of how far the center of gravity or point 26 is away from the coordinate center along the center line 20 of the container 10 (FIG. 2). The asymmetry of the nozzle end (FIG. 3) does not significantly displace the center of gravity point 26 from the center line 20. The y coordinate of the point where the critical line and the center line intersect is given by:

Y_(critical) = r_(max)tan  θ ${{Where}\mspace{14mu} \theta} = {\tan^{- 1}\left( \frac{r_{\max} - r_{flange}}{L + n} \right)}$

Less than Full Container Stability

When the container 10 is less than full, the center of gravity position or point 26 will shift with the container tilt angle and fluid level. It is possible for the center of gravity or point 26 to shift in the negative y direction as the fluid level drops. The center of gravity shifts in the positive y direction for most geometries. This results in an increased positive restoring moment. Fluid levels less than full will also cause the center of gravity to shift off the center line 20 when the container is tilted. Any displacement of the center of gravity from the center line 20 is of no concern since it will be in a direction resulting in an increased restoring moment as seen in FIG. 9. Thus, the center of gravity shifts along centerline 20 in the direction of arrow 33 and off centerline 20 in the direction of arrow 34.

The y coordinate of the shifted center of gravity must be checked for various fluid levels to assure it is not less than y critical. This need only be done for the bottle tipped completely on its side as this is the worst case. When recalculating the y shift in the center of gravity, only the integrating of the fluid sections of the container must be repeated.

Partially Filled Stem Section

To integrate the stem section 12, 13, an expression for the fluid level along the stem section 12, 13 is required. The problem now becomes a double integral. Integration must be performed along the center line 20 and across each section 12, 13 (FIGS. 10 and 11). The integral for the center of gravity of the stem section 12, 13 now becomes:

${\overset{\_}{y}}_{stem} = \frac{\int_{0}^{L}{y{\int_{- r}^{xf}{2\sqrt{r^{2} - x^{2}}{x}{y}}}}}{\int_{0}^{L}{\int_{- r}^{xf}{2\sqrt{r^{2} - x^{2}}{x}{y}}}}$

where for the curved portion of the stem section 12, 13:

$r = {{\left( {r_{\max} - r_{cap}} \right)\left\lbrack {a - {b\left( \frac{y}{L} \right)} + {c\left( \frac{y}{L} \right)}^{2} - {d\left( \frac{y}{L} \right)}^{3} + {e\left( \frac{y}{L} \right)}^{4}} \right\rbrack} + r_{cap}}$

and for the straight portion of the stem section 12, 13:

r=r_(cap)

The mass of fluid in the stem section is given by:

m _(stem)=ρ_(fluid)∫₀ ^(L)∫_(−r) ^(xf)2√{square root over (r ² −x ²)}dxdy

Partially Filled Fluid Base Portion

The integral for the center of gravity of the fluid base portion 11 for a partially filled container now becomes:

$y_{{fluid}\mspace{14mu} {base}} = \frac{\int_{0}^{r_{\max} - h}{y{\int_{- r}^{xf}{2\sqrt{r^{2} - x^{2}}{x}{y}}}}}{\int_{0}^{r_{\max} - h}{\int_{- r}^{xf}{2\sqrt{r^{2} - x^{2}}{x}{y}}}}$

where for the fluid base r²=r² _(max)−y²

The mass of fluid in the fluid base section is given by:

m _(fluid base)=ρ_(fluid)∫₀ ^(r max−h)∫_(−r) ^(xf)2√{square root over (r ² −x ²)}dxdy

Computer Aided Design

A BASIC computer program is used to aid in the bottle design (Appendix A). The program is divided into two parts. The first part of the program provides various bottle geometries that yield a positive restoring moment for a full bottle lying on its side. A total fluid volume of the bottle must be specified within the program listing. The fixed variables in the program are y_(cap), n (length of the straight portion of the stem section), P_(fluid), P_(weight), r_(flange), y_(cap), m_(cap) and V_(total). The first part of the program searches through a range of L, t, r_(max), and r_(base). All geometries that provide a positive restoring moment for a total volume within a specified error are listed in the output.

The second part of the program analyzes the shift of the center of gravity in the y direction for various levels of fluid. This section of the program requires a given bottle geometry. The center of gravity analysis is for a bottle tipped completely on its side. The user must input L, t, r_(max), and r_(base). Fluid levels are incremented along the f axis (FIG. 10). The variable x_(f) is expressed in terms of f, the fluid level, as:

${x_{f}\frac{f}{\cos \; \theta}} - {y\; \tan \; \theta}$

The program solves for the y coordinate of the center of gravity for fluid levels ranging from a full bottle, where f=r_(max), to an empty bottle, where f=−r_(max) cos θ. The number of fluid levels and the number of integration steps can be changed in the program listing.

Results

As a trial run of the computer program a target volume of 16 ounces was chosen. Table 2 gives a list of the specific values and range of values used for various bottle parameters. Twenty (20) integration steps and ten (10) fluid level steps were used for this trial.

TABLE 2 Trial variables Nomenclature Value/Range Step Size r_(max) 2.00-2.20 [in] 0.05 [in] t 0.40-1.00 [in] 0.05 [in] V 16 [oz] +1.0 [oz] r_(cap) 0.5 [in] — L 4.50-5.00 [in] 0.05 [in] r_(base) 0.50-2.15 [in] 0.05 [in] m_(cap) 0.01 [lbs] —

The computer output for the trial run is provided in Appendix B. The output shows that a variety of bottle geometries will work. A number of points must be considered in selecting a specific bottle geometry.

The empty weight of the container must not be excessive to make handling of the container awkward. The base radius should be as large as possible to make tipping the container over as difficult as possible.

Table 2 lists the container geometry selected from the trial output of Appendix B for a detailed y coordinate center of gravity analysis. The computer output from this analysis is provided in FIG. 12 wherein:

-   -   Hemisphere radius [in]=2.00     -   Stem height [in]=4.90     -   Base radius [in]=0.60     -   Weight thickness [in]=0.55     -   Total fluid volume [oz]=0.00     -   Total weight [lbs]=0.94     -   Empty weight [lbs]=0.94     -   Delta y [in]=1.02     -   Center of gravity [in]=1.48     -   Scale: one inch

TABLE 2 Selected trial container geometry Variable Value/Range R_(max) 2.00 [in] t 0.55 [in] V 16.2 [oz] r_(cap) 0.5 [in] L 4.90 [in] r_(base) 0.60 [in]

CONCLUSIONS

The analysis of the center of gravity shifts for a container with the dimensions given in Table 2 showing it to have a positive restoring moment for all fluid levels. The empty weight for this container is 0.94 pounds. The minimum distance between the center of gravity and the critical line is 0.011 inches. Although the analysis is considered conservatively, the tolerance for the manufacture of this container would be strict.

The total volume for the trial container is 16.2 ounces. This volume represents the total interior volume of the container. The actual fluid should be less than the total container volume.

It can be seen that there is described a container 10 in the preferred form of a bottle that can right itself after being tipped. This substantially reduces spillage. The container 10 includes a smooth tapered section 13 with a truncated hemispherical base portion 11. The weighted bottom member 19 assists container 10 in righting itself. In order to minimize the weight required to make container 10 self righting, a flange is preferably provided just below cap 15. The flange 18 limits the angle at which container 10 rests when it is tipped completely on its side as seen in FIG. 2.

APPENDIX B hemisphere stem base weight fluid full empty center of radius height radius thickness volume weight weight delta y gravity [in] [in] [in] [in] [oz.] [lbs] [lbs] [in] [in] 2.00 4.70 0.50 0.55 16.01 1.92 0.87 0.005 0.49 2.00 4.75 0.50 0.55 16.09 1.92 0.87 0.001 0.48 2.00 4.75 0.55 0.55 16.04 1.95 0.90 0.013 0.49 2.00 4.80 0.55 0.55 16.13 1.95 0.90 0.0 0.48 2.00 4.80 0.60 0.55 16.07 1.99 0.94 0.0 0.49 2.00 4.80 0.75 0.5 16.06 1.96 0.92 0.0 0.47 2.00 4.85 0.55 0.55 16.21 1.96 0.90 0.0 0.47 2.00 4.85 0.60 0.55 16.15 1.99 0.94 0.0 0.48 2.00 4.90 0.60 0.55 16.23 2.00 0.94 0.011 0.48 2.05 4.50 0.50 0.55 16.63 1.98 0.89 0.020 0.55 2.05 4.50 0.70 0.5 16.59 1.98 0.89 0.012 0.55 2.05 4.50 0.90 0.45 16.46 1.99 0.92 0.004 0.54 2.05 4.55 0.50 0.55 16.72 1.98 0.89 0.017 0.54 2.05 4.55 0.70 0.5 16.68 1.98 0.89 0.009 0.54 2.05 4.60 0.50 0.55 16.80 1.99 0.89 0.013 0.54 2.05 4.60 0.70 0.5 16.76 1.99 0.89 0.005 0.53 2.05 4.65 0.50 0.55 16.89 1.99 0.89 0.009 0.53 2.05 4.65 0.70 0.5 16.85 1.99 0.89 0.001 0.52 2.05 4.70 0.50 0.55 16.97 2.00 0.89 0.005 0.52 

1. A self righting fluid containing container comprising: a base portion having a flat bottom and a hollow fluid holding interior; a neck portion having a throughbore; a tapered section having a throughbore interconnecting said throughbore through said neck portion to said interior of said base portion; a cap closing off said neck portion, an integral outwardly extending peripheral flange of a diameter greater than the diameter of said neck portion mounted on said neck portion; and a weighted member disposed in said base portion, the center of gravity of said container being located on the positive side of a critical line extending from a point at the intersection of said base portion with said tapered section when said container is inclined on a supporting surface from said supporting surface and generally normal to the plane of said supporting surface, said center of gravity also being located along the centerline of said container, away from said critical line and toward said weighted portion.
 2. In the container of claim 1 wherein said flange is integral with said cap.
 3. In the container of claim 1 wherein the centerline of said container makes an angle a with the plane of said supporting surface, said critical line also making an angle a with a line extending from said point to the uppermost point where said tapered section intersects with said base portion when said container is inclined on said supporting surface.
 4. In the container of claim 1 wherein said base portion is a truncated hemispherical shaped section.
 5. In the container of claim 1 wherein the outer surface of said base portion smoothly curves from said bottom up to the intersection with said tapered section.
 6. In the container of claim 1 wherein said container is thin walled throughout.
 7. In the container of claim 1 wherein said container is of a high density material.
 8. In the container of claim 7 wherein said container is of lead.
 9. In the container of claim 1 wherein the center of gravity of said container and any fluid contained therein is given by: $y = \frac{\Sigma \; y_{i}m_{i}}{\Sigma \; m_{i}}$ where i=material of said container y_(i)=is distance to center of gravity of i as measured from the coordinate center of said container m_(i)=is the mass of i.
 10. In the container of claim 1 wherein said neck portion is threaded at a threaded portion and the mass of said neck portion and said flange is given by: m _(f/t)=ρ_(container)π(t _(f)(r ² _(flange) −r ² _(cap)+2kzr _(cap)) where ρ_(container)=density of the material of said container and tf=flange thickness r_(flange)=flange radius r_(cap)=means radius of said neck portion z=height of the threads of said neck portion k=means thickness of said threaded point.
 11. In the container of claim 10 wherein the center of gravity of said cap relative to the coordinate center of said container is given by: y _(cap)=1+L+n when n=length of threaded portion L=distance from uppermost end of said threaded portion to the bottom of said container.
 12. In the container of claim 11 wherein said cap includes a spray nozzle portion and the total mass of said cap, said flange and said spray nozzle portion is given by: m _(cap) =m _(nozzle) +m _(f/t) where m_(nozzle)=mass of said spray nozzle portion and m_(f/t)=mass of flange thickness.
 13. In the container of claim 1 wherein said tapered section has a straight portion integral with said neck portion and the total mass of said neck portion and the straight portion of said tapered section is given by: m_(stem)=m_(stem curve)=mass of the tapered section excluding said straight portion and m_(stem straight)=mass of said straight portion.
 14. In the container of claim 13 wherein the center of gravity of said neck portico and said straight portion of said tapered section is given by: where: y_(stem straight)=center of gravity of said straight portion of said tapered section y_(stem curved)=center of gravity of said tapered section excluding said straight portion.
 15. In the container of claim 14 wherein the center of gravity of said container and any fluid contents is given by: ${\overset{\_}{y}}_{bottle} = \frac{{{- {\overset{\_}{y}}_{cap}}m_{cap}} - {{\overset{\_}{y}}_{stem}m_{stem}} + {{\overset{\_}{y}}_{{fluid}\mspace{14mu} {base}}m_{{fluid}\mspace{14mu} {base}}} + {{\overset{\_}{y}}_{weight}m_{weight}}}{m_{cap} + m_{stem} + m_{{fluid}\mspace{14mu} {base}} + m_{weight}}$ where y_(cap)=center of gravity of said cap m_(cap)=mass of said cap y_(stem)=center of gravity of said neck portion and said straight portion m_(stem)=mass of said neck portion and said straight portion y_(fluid base)=center of gravity of said fluid within said base portion m_(fluid base)=mass of said fluid within said base portion y_(weight)=center of gravity of said weighted member m_(weight)=mass of said weighted member m_(cap)=mass of said cap. 